We present K-band spectra of rest-frame optical emission lines for 24
star-forming galaxies at z~3.2-3.7 using MOSFIRE on the Keck 1 telescope.
Strong rest-frame optical O III and Hbeta emission lines were detected in 18
LBGs. The median flux ratio of O III5007 to Hbeta is 5.1+/-0.5, a factor of
5-10x higher than in local galaxies with similar stellar masses. The observed
Hbeta luminosities are in good agreement with expectations from the estimated
star-formation rates, and none of our sources are detected in deep X-ray
stacks, ruling out significant contamination by active galactic nuclei.
Combining our sample with a variety of LBGs from the literature, including 49
galaxies selected in a very similar manner, we find a high median ratio of
OIII/Hbeta = 4.8+0.8-1.7. This high ratio seems to be an ubiquitous feature
of z~3-4 LBGs, very different from typical local star-forming galaxies at
similar stellar masses. The only comparable systems at z~0 are those with
similarly high specific star-formation rates, though ~5x lower stellar masses.
High specific star-formation rates either result in a much higher ionization
parameter or other unusual conditions for the interstellar medium, which result
in a much higher OIII/Hbeta line ratio. This implies a strong relation
between a global property of a galaxy, the specific star-formation rate, and
the local conditions of ISM in star-forming regions.
Description
[1401.5490] Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected Galaxies: The Ubiquity of Unusually High [OIII]/Hbeta Ratios at 2 Gyr
%0 Generic
%1 holden2014restframe
%A Holden, B. P.
%A Oesch, P. A.
%A Gonzalez, V. G.
%A Illingworth, G. D.
%A Labbe, I.
%A Bouwens, R.
%A Franx, M.
%A van Dokkum, P.
%A Spitler, L.
%D 2014
%K emission galaxy highz lines metallicity sfr
%T Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected
Galaxies: The Ubiquity of Unusually High OIII/Hbeta Ratios at 2 Gyr
%U http://arxiv.org/abs/1401.5490
%X We present K-band spectra of rest-frame optical emission lines for 24
star-forming galaxies at z~3.2-3.7 using MOSFIRE on the Keck 1 telescope.
Strong rest-frame optical O III and Hbeta emission lines were detected in 18
LBGs. The median flux ratio of O III5007 to Hbeta is 5.1+/-0.5, a factor of
5-10x higher than in local galaxies with similar stellar masses. The observed
Hbeta luminosities are in good agreement with expectations from the estimated
star-formation rates, and none of our sources are detected in deep X-ray
stacks, ruling out significant contamination by active galactic nuclei.
Combining our sample with a variety of LBGs from the literature, including 49
galaxies selected in a very similar manner, we find a high median ratio of
OIII/Hbeta = 4.8+0.8-1.7. This high ratio seems to be an ubiquitous feature
of z~3-4 LBGs, very different from typical local star-forming galaxies at
similar stellar masses. The only comparable systems at z~0 are those with
similarly high specific star-formation rates, though ~5x lower stellar masses.
High specific star-formation rates either result in a much higher ionization
parameter or other unusual conditions for the interstellar medium, which result
in a much higher OIII/Hbeta line ratio. This implies a strong relation
between a global property of a galaxy, the specific star-formation rate, and
the local conditions of ISM in star-forming regions.
@misc{holden2014restframe,
abstract = {We present K-band spectra of rest-frame optical emission lines for 24
star-forming galaxies at z~3.2-3.7 using MOSFIRE on the Keck 1 telescope.
Strong rest-frame optical [O III] and Hbeta emission lines were detected in 18
LBGs. The median flux ratio of [O III]5007 to Hbeta is 5.1+/-0.5, a factor of
5-10x higher than in local galaxies with similar stellar masses. The observed
Hbeta luminosities are in good agreement with expectations from the estimated
star-formation rates, and none of our sources are detected in deep X-ray
stacks, ruling out significant contamination by active galactic nuclei.
Combining our sample with a variety of LBGs from the literature, including 49
galaxies selected in a very similar manner, we find a high median ratio of
[OIII]/Hbeta = 4.8+0.8-1.7. This high ratio seems to be an ubiquitous feature
of z~3-4 LBGs, very different from typical local star-forming galaxies at
similar stellar masses. The only comparable systems at z~0 are those with
similarly high specific star-formation rates, though ~5x lower stellar masses.
High specific star-formation rates either result in a much higher ionization
parameter or other unusual conditions for the interstellar medium, which result
in a much higher [OIII]/Hbeta line ratio. This implies a strong relation
between a global property of a galaxy, the specific star-formation rate, and
the local conditions of ISM in star-forming regions.},
added-at = {2014-01-23T10:03:15.000+0100},
author = {Holden, B. P. and Oesch, P. A. and Gonzalez, V. G. and Illingworth, G. D. and Labbe, I. and Bouwens, R. and Franx, M. and van Dokkum, P. and Spitler, L.},
biburl = {https://www.bibsonomy.org/bibtex/21c1502a32f5939149241f6f679ff1511/miki},
description = {[1401.5490] Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected Galaxies: The Ubiquity of Unusually High [OIII]/Hbeta Ratios at 2 Gyr},
interhash = {d92e73e80402f514b6d0847df140e27c},
intrahash = {1c1502a32f5939149241f6f679ff1511},
keywords = {emission galaxy highz lines metallicity sfr},
note = {cite arxiv:1401.5490Comment: 13 pages, 8 figures, 5 color, submitted to ApJ},
timestamp = {2014-01-23T10:03:15.000+0100},
title = {Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected
Galaxies: The Ubiquity of Unusually High [OIII]/Hbeta Ratios at 2 Gyr},
url = {http://arxiv.org/abs/1401.5490},
year = 2014
}